Reduce repository code through refactoring and consolidation

Identify top 5 opportunities to massively reduce the amount of code (lines of code) in any part of the repo: - Similar functionality that can be unified and reused - Code that has been valuable but no more - A front end component or a group of them duplicate another component/page functionality. Use the most modern and nice looking - etc. Now implement them :)

Five retirements on live evidence, net −215 lines: the agent-plane project-by-name fallback (census: all nodes ≥1.2.4842; daemon now reports known slots by id), HIPAA crosswalk folded into the ISO engine, two zero-row windows (pre-0179 tailnet name guard, legacy DeepSeek id), the flag-less vnode wire, 10 web writes onto useSubmit. Review lane pass (4 findings fixed, verified). Quick gate pass; PR #7443 queued in the merge lane. No massive cut exists without a product decision; four named in the report.